This invention is related to a method and system of half-duplex wireless messaging or communication that minimizes collision of messages among the mobile stations to and from a base station.
Wireless messaging and communication systems would be advantageous for use in offices, large premises and other similar locations. Such wireless messaging and communication systems would facilitate installation because hardwired systems would not be necessary as is common with many types of LAN and e-mail systems. A wireless messaging and communication system can also be connected almost anywhere within the office or premises.
It would be advantageous if an indoor, premises based wireless communication system could be implemented that would allow messaging among various users in the premises or office. Preferably, such communication or messaging system would be inexpensive compared to LAN based systems and would use minimal power and operate at a minimal cost.
In accordance with the present invention, a wireless communication and messaging system is a half-duplex system where a premises has a base station that services a defined communication cell such as an office space. The base station transmits and receives Request to Send and Clear to Send announcements to and from mobile stations to indicate that the base station can send and receive data such as messages to and from the mobile stations. A plurality of mobile stations send and receive data after transmitting and receiving Request to Send and Clear to Send announcements to and from the base station based on the respective time period that the base station received the Request to Send and Clear to Send announcements from respective mobile stations.
In accordance with one aspect of the present invention, the base station transmits to a plurality of mobile stations contained within one wireless communication cell a READY announcement indicating that the base station is ready to receive data on an uplink channel from the mobile stations. A random initial backoff time is set for each mobile station. A Request to Send announcement is then transmitted from each mobile station to the base station following expiration of the backoff time period. The base station then transmits to the mobile stations a Clear to Send announcement indicating that a first mobile station had its Request to Send announcement received in the base station before the other mobile stations and that first mobile station can now transmit data. That mobile station then transmits its data. The other mobile stations then resubmit their Request to Send announcements after a predetermined backoff time period has expired. That backoff time period corresponds to a time period in which the first mobile station can transmit its data to the base station.
The downlink protocol for sending messages from the base station to a mobile station is less complex than that uplink protocol for sending messages from the mobile stations to the base station. The base station will send a Request To Send to the mobile stations. Then, the base station will wait for the Clear To Send and then begin sending.